The present invention relates to a semiconductor device manufacturing technique. More particularly, the present invention is concerned with a molding technique for sealing electronic parts, such as semiconductor chips that are mounted on a wiring substrate, with a resin.
In a molding step included in a semiconductor device manufacturing process, a lead frame and a wiring substrate, having such electronic parts as semiconductor chips mounted thereon, are accommodated within a molding die, and then resin is injected into a cavity of the molding die to form a resin sealing member which covers and protects the electronic parts. In the case where the member which carries the electronic parts thereon is a lead frame, it is not so necessary to change the molding die because the thickness of the lead frame is almost constant. However, in the case where the electronic parts-carrying member is a wiring substrate, there is a tendency toward diversification of the type of member with adoption of a stacked structure of semiconductor chips and improvement of the packaging density; and, since the thickness of the resin sealing member and that of the wiring substrate may vary, there arises the necessity of changing the molding die accordingly. As to the case where the thickness of the resin sealing member differs, since this does not involve so many changes, a molding portion is newly fabricated to cope with production. However, the thickness of the wiring substrate differs for each type, and the range of thickness error is large due to the stacked structure of the wiring layers. Thus, it is impossible to take a satisfactory countermeasure to solve this dilemma. Therefore, even for similar products, it is necessary to fabricate a suitable molding die for each of the resin sealing members having different thicknesses. Further, it is necessary to provide molding dies to match the different thicknesses of the wiring substrates for different thicknesses of the resin sealing members. As a result, not only do new investment and product costs increase, but also the period required for the development of the product becomes longer. As a countermeasure, there is a known lower die elastic structure technique wherein a lower die of a molding die is supported vertically so as to be movable by means of an elastic member, such as a spring. According to this technique, in a molding step using the molding die, an upper surface of an outer peripheral edge of a wiring substrate placed on the lower die is held down by the upper die to sandwich the wiring substrate in between the upper and lower dies, and then resin is injected into a cavity of the molding die. In this case, since the lower die is supported vertically so as to be movable, when the wiring substrate is pushed down by the upper die, the lower die can be moved vertically in accordance with the thickness of the wiring substrate. Thus, a variation in thickness of the wiring substrate can be absorbed by the vertical movement of the lower die.
For example, Japanese Unexamined Patent Publication No. 2001-223229 discloses a construction wherein a wiring substrate block with a wiring substrate mounted thereon is supported vertically so as to be movable by a floating mechanism which utilizes a spring (see Patent Literature 1).
Also, for example, Japanese Unexamined Patent Publication No. 2000-58571 discloses a technique wherein a clamp block for pressing a substrate is provided in a molding die, and control is effected so as to exert an optimal pressing force of the clamp block against the substrate (see Patent Literature 2).
Further, for example, Japanese Unexamined Patent Publication No. Hei 10 (1998)-92853 discloses a technique wherein the degree of opening of each air vent is adjusted for suppressing the formation of voids or the like due to resin clogging of air vents in a molding die during sealing with resin (see Patent Literature 3).                [Patent Literature 1]        Japanese Unexamined Patent Publication No. 2001-223229        [Patent Literature 2]        Japanese Unexamined Patent Publication No. 2000-58571        [Patent Literature 3]        Japanese Unexamined Patent Publication No. Hei 10 (1998)-92853        